Human growth and consumerism are overloading freshwater systems with pesticides, antibiotics, pharmaceuticals, and personal care products (APPCPs). The rapid expansion of agricultural chemicals and uneven regulatory enforcement of water management in human settlements exacerbate environmental toxicity.
Mexico’s rapidly evolving agro-urban landscapes are experiencing increasing pressures from agricultural intensification, urban expansion, and wastewater generation. A recent study has detected neonicotinoids across complex water systems in the land use where we eat and live. A neonicotinoid is a systemic agricultural insecticide that resembles nicotine. Its overuse is among the causes of this insecticide persisting in rivers, wastewater discharges, and groundwater. The study by a group of researchers led by Faculty of Excellence Professor Dr. Manish Kumar at Tecnologico de Monterrey contributes to understanding how neonicotinoids are transported at trace concentrations in México (Kumar et al., in preprint, 2026).
The principal innovation of the study is the demonstration that commonly monitored water-quality indicators such as nitrate, nitrite, sulfate, iron, and copper can serve as practical proxy indicators for neonicotinoid contamination. This relationship offers a cost-effective screening approach for regions where direct pesticide monitoring is limited.
Several studies have documented the continued use of highly hazardous pesticides across food production systems and have detected residues of these substances in fruits and vegetables. Compared with previous works in which most monitoring and risk assessment frameworks treat these compounds as independent, this latest study provides an integrative indicator of pesticide occurrence and a link to fertilization practices.
A new way to detect pesticide contamination
The chemical compositions of water containing nitrate, nitrite, sulfate, iron (Fe), copper (Cu), and pesticides, particularly neonicotinoids, remain poorly characterized, especially in agricultural watersheds and cities where agricultural runoff and urban activities intersect. This knowledge gap hinders the development of cost-effective screening approaches to identify freshwater systems vulnerable to pesticide contamination in regions with limited monitoring data.
The present study addresses this gap by providing a coordinated assessment of neonicotinoid pesticides and APPCPs across interconnected freshwater systems, including rivers, wastewater, and groundwater in northern and central Mexico.
This work helps identify sources of pollution associated with agricultural production. The analyses show that nutrient concentrations can serve as practical indicators of neonicotinoid occurrence in agricultural and urban settings, creating opportunities for more efficient environmental monitoring in regions with limited analytical capacity.
The study quantified pesticides and APPCPs in selected Mexican water bodies, characterized spatial contamination patterns, evaluated relationships among contaminants and transformation products, investigated nutrient-based hydrochemical proxies, and assessed ecological risks. Together, these analyses provide a framework for understanding contaminant mixtures and risk propagation.
The hydraulic connectivity in catchments with multiple land uses results in a combination of source compositions and transformation products, with moderate neonicotinoid residues associated with persistent pharmaceutical compounds. This mixed contamination problem is increasingly reported in expanding agro-industrial zones in Mexico and facilitates the emergence of antimicrobial resistance.
Pesticides to grow food and harm humans too
Mexico is a large consumer of neonicotinoids in Latin America. Neonicotinoids include thiamethoxam, clothianidin, imidacloprid, and acetamiprid, a leading class of insecticides used in croplands. These compounds are frequently detected in surface water and groundwater. Selective insecticides such as imidacloprid, thiamethoxam, clothianidin, and their metabolites pose greater toxicity concerns and complicate environmental recovery.
The toxicological effects of neonicotinoids come from their accumulation in produce and their potential to threaten pollination. The toxicity burden is often borne by vulnerable groups, especially children and workers in agricultural communities.
Contamination extends beyond agricultural products and bottled water supplies to aquatic organisms harvested for food. Exposure to these substances has been associated with altered inflammatory and hematological responses in previous studies.
Previous studies in Mexico have examined several river basins; however, these new findings are consistent with prior evidence of intensive pesticide use in northern Mexico. Transport and detection of pesticide concentrations are associated with irrigation networks and early-season rainfall events.
APPCPs and wastewater pollution
Mexico reveals growing contamination of APPCPs in highly urbanized watersheds, indicating incomplete removal by municipal treatment plants. Municipal wastewater from hospitals, household sewage, and livestock facilities contains antibiotics, pharmaceuticals, personal care products, and wastewater tracers such as sucralose. Their detection is strongly associated with wastewater discharges, runoff enriched with fertilizers and pesticides, and discharges from industrial zones and peri-urban settlements. Herbicides such as 2,4-D, diuron, and metolachlor are commonly detected with APPCPs. During the dry season, reduced river flow and evaporation can further intensify APPCP concentrations. Also, the structure of the underground creates natural boundaries that isolate groundwater from direct contamination, unlike surface water bodies.
Where in México was water pollution detected?
The locations in this analysis span a gradient of agricultural, industrial, municipal, and relatively low-impact hydrogeological settings, encompassing river systems, wastewater effluents, and groundwater environments across northern and central Mexico. Cases discussed in the study include the Río Lerma basin near Toluca, the Maya region of the Yucatán Peninsula, the San Juan–Pesquería River system and its wastewater treatment plant in Nuevo León, a river flowing into Lake Texcoco influenced by peri-urban runoff, and groundwater from agricultural areas near Querétaro.
River stretches influenced by agriculture exhibited the highest loads of neonicotinoids and their transformation products, whereas wastewater-impacted reaches were dominated by sulfonamides, macrolides, quinolones, and persistent wastewater tracers. Groundwater contained only trace contaminants, indicating strong natural attenuation. The concentrations of Fe and Cu are associated with pesticides and fungicides, indicating that these metals may be mobilized through fertilizer impurities and nutrient enrichment in soils. Fertilizer–pesticide coupling intensifies in zones of active agriculture, and concentrations of nitrate, nitrite, sulfate, and urea can serve as environmental markers of pesticide occurrence in agricultural surface waters.
Imminent risk exposure
The lack of integrated chemical surveillance is particularly problematic in vulnerable semi-arid agro-urban regions, where agricultural runoff and municipal discharges converge. Despite the predominance of neonicotinoids and multiple antibiotic classes, most compounds remained at low ecological risk, although several neonicotinoid transformation products showed localized moderate risk. Certain compounds may still pose local concerns and should not be overlooked in risk evaluations.
The concurrent presence of hydrophilic pesticides, antibiotic residues, and persistent metabolites, together with their strong co-occurrence patterns, suggests the possibility of chronic effects that conventional single-compound risk assessments may not capture. Detection of dominant compounds such as clothianidin and sulfamethoxazole supports the need for long-term monitoring.
Overall, these findings highlight the need for integrated pesticide and pharmaceutical monitoring programs that track parent compounds and metabolites, assess mixture toxicity, incorporate hydrological connectivity, strengthen wastewater treatment performance, and support One Health–based environmental management approaches.
Next alternative opportunities
Beyond identifying contamination patterns, the findings may help guide future monitoring and management strategies for pollution mitigation, site recovery, and remediation. Because nutrient indicators are routinely measured in many water-quality programs, they could provide an accessible way to identify locations vulnerable to pesticide contamination before more detailed chemical analyses are conducted. Other possible strategies may enhance natural attenuation processes, improve water quality, and support healthier aquatic environments.
